KR20080062406A - Liquid crystal display device - Google Patents

Abstract

An LCD(Liquid Crystal Display) is provided to form an insulating layer on upper and lower substrates respectively including a common electrode and a pixel electrode to prevent generation of leakage current and reduce the thickness of an alignment film. An LCD includes upper and lower substrates(30,40) opposite to each other, a common electrode(31), a pixel electrode(41), first and second insulating layers(32,42), first and second alignment films(33,43), and a liquid crystal layer(35) interposed between the upper and lower substrates. The common electrode is formed on the upper substrate. The pixel electrode is formed in each pixel region on the lower substrate. The first and second insulating layers are respectively formed on the upper and lower substrates and respectively cover the common electrode and the pixel electrode. The first and second insulating layers are formed of an inorganic insulating material. The first and second alignment films are respectively formed on the upper and lower substrates.

Description

Liquid Crystal Display Device

1 is an exploded perspective view showing a part of a typical TN liquid crystal display device

2 is a schematic structural cross-sectional view of a liquid crystal display according to the related art.

3 is a schematic structural cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

30: upper substrate 31: common electrode

32: first electrical insulating layer 33: first alignment layer

34: upper polarizing plate 40: lower substrate

41: pixel electrode 42: second electrical insulating layer

43 second alignment layer 44 lower polarizing plate

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device suitable for securing the stability of liquid crystal driving by blocking leakage current generation.

As the information society develops, the demand for display devices is increasing in various forms.In recent years, liquid crystal display (LCD), plasma display panel (PDP), electro luminescent display (ELD), and vacuum fluorescent display (VFD) have been developed. Various flat panel display devices have been studied, and some of them are already used as display devices in various devices.

Among them, LCD is the most widely used as a substitute for CRT (Cathode Ray Tube) for the use of mobile image display device because of the excellent image quality, light weight, thinness, and low power consumption, and mobile type such as monitor of notebook computer. In addition, it is being developed in various ways, such as a television for receiving and displaying broadcast signals, and a monitor of a computer.

As described above, although various technical advances have been made in order for the liquid crystal display device to serve as a screen display device in various fields, the task of improving the image quality as the screen display device has many advantages and disadvantages.

Therefore, in order for a liquid crystal display device to be used in various parts as a general screen display device, development of high quality images such as high definition, high brightness, and large area is maintained while maintaining the characteristics of light weight, thinness, and low power consumption. It can be said.

Such a liquid crystal display device may be broadly divided into a liquid crystal panel displaying an image and a driving unit for applying a driving signal to the liquid crystal panel, wherein the liquid crystal panel includes first and second glass substrates having a space and are bonded to each other; It consists of a liquid crystal layer injected between the said 1st, 2nd glass substrate.

Hereinafter, a configuration of a general liquid crystal display device will be described with reference to the accompanying drawings.

1 is an exploded perspective view illustrating a part of a general TN liquid crystal display device.

As shown in FIG. 1, a general TN liquid crystal display device includes a lower substrate 1 and an upper substrate 2 bonded to each other with a predetermined space, and a liquid crystal injected between the lower substrate 1 and the upper substrate 2. It consists of layer (3).

More specifically, the lower substrate 1 has a plurality of gate lines 4 arranged in one direction at regular intervals to define the pixel region P, and in a direction perpendicular to the gate lines 4. A plurality of data lines 5 are arranged at regular intervals to be arranged to define the pixel region P, and pixels are formed in each pixel region P defined by crossing the gate line 4 and the data line 5. The electrode 6 is formed, and the thin film transistor T is formed at a portion where the gate lines 4 and the data lines 5 intersect each other.

The upper substrate 2 includes a black matrix layer 7 for blocking light in portions other than the pixel region P, an R, G, and B color filter layer 8 for expressing color colors, and an image. The common electrode 9 is formed to implement the.

The pixel electrode 6 uses a transparent conductive metal having a relatively high light transmittance, such as indium-tin-oxide (ITO).

In the liquid crystal display device configured as described above, the liquid crystal layer 3 positioned on the pixel electrode 6 is aligned by a signal applied from the thin film transistor T, and the liquid crystal layer 3 is aligned with the alignment degree of the liquid crystal layer 3. Accordingly, the image can be expressed by controlling the amount of light passing through the liquid crystal layer 3.

As described above, the liquid crystal panel drives the liquid crystal by an electric field applied up and down, and has excellent characteristics such as transmittance and aperture ratio, and the common electrode 9 of the upper substrate 2 serves as a ground to discharge static electricity. It is possible to prevent the destruction of the liquid crystal cell.

Hereinafter, a schematic cross-sectional view of a liquid crystal display according to the related art will be described with reference to the accompanying drawings.

2 is a schematic structural cross-sectional view of a liquid crystal display according to the prior art.

Referring to FIG. 2, a liquid crystal display according to the related art is schematically illustrated. As shown in FIG. 2, the transparent upper and lower substrates 10 and 20 facing each other with the liquid crystal layer 15 disposed therebetween and the upper substrate ( A common electrode 11 formed on the inner surface of the substrate 10, a pixel electrode 21 formed on each pixel region of the inner surface of the lower substrate 20, and an inner front surface of the upper and lower substrates 10 and 20. The first and second alignment layers 12 and 22 formed thereon and the upper and lower polarizing plates 13 and 23 formed on the respective outer surfaces of the upper and lower substrates 10 and 20, respectively.

The pixel electrode 21 and the common electrode 11 are formed of a transparent conductive film such as indium tin oxide (ITO).

The first and second alignment layers 12 and 22 are made of an organic material such as polyimide or a photo-alignment material, and have a thickness of about 700 to 1000 Å.

Here, the alignment layer made of polyimide is determined by mechanical rubbing, and the photoreactive material made of polyvinylcinnamate based material or polysiloxane based material is oriented by irradiation with light such as ultraviolet rays. The direction is determined.

At this time, the alignment of the liquid crystal is determined by the irradiation direction of light or the property of the irradiated light, that is, the polarization direction.

In this case, the first and second alignment layers 12 and 22 not only determine the alignment direction of the liquid crystal but also prevent leakage current when a voltage is applied between the pixel electrode 21 and the common electrode 11 for driving the liquid crystal. It is formed for the role.

However, the conventional liquid crystal display device configured as described above has the following problems.

First, when the first and second alignment layers 12 and 22 are made of a polymer material such as polyimide (PI), PI is inferior to an inorganic insulating layer such as silicon nitride film or silicon oxide film, and thus is shown in FIG. 2. As described above, leakage current may be generated to cause residual DC in the liquid crystal layer 15, or may be a factor of changing the capacitance value of the liquid crystal layer in a design. Accordingly, it is possible to affect the liquid crystal drive and lower the image quality.

Second, the liquid crystal layer made of an organic material may cause various undesired side reactions due to the movement of electrons even with a small current. As described above, since the first and second alignment layers 12 and 22 have low insulation properties, Side reactions can lead to an increase in ionic impurities.

Accordingly, there is a problem that various defects occur in the LCD panel.

The present invention has been made to solve the above problems, an object of the present invention is to provide a liquid crystal display device suitable for securing the stability of the liquid crystal drive by blocking the leakage current generation.

Liquid crystal display device according to the present invention for achieving the above object is provided with a liquid crystal layer between the upper and lower substrates and facing; A common electrode formed on an inner upper portion of the upper substrate; A pixel electrode formed in each pixel area on the inner upper side of the lower substrate; First and second electrical insulating layers formed on the inner upper portions of the upper and lower substrates, respectively; And first and second alignment layers formed on an inner upper front surface of the upper and lower substrates including the first and second electrical insulating layers.

The first and second electrical insulating layers are made of an inorganic insulating film such as an inorganic oxide film and have a thickness of 50 to 100 kPa or less.

The pixel electrode may be formed to have a thickness of about 1000 to 1500 mW, and the first and second alignment layers may have a thickness of about 700 to 1000 mW.

The common electrode and the pixel electrode may be formed of indium tin oxide (ITO), tin oxide (TO), indium zinc oxide (IZO), or indium tin zinc oxide (ITZO). It is composed of a transparent conductive film such as).

The first and second alignment layers are made of organic material such as polyimide or photo-alignment material.

Hereinafter, a liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

3 is a schematic structural cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

In the liquid crystal display according to the exemplary embodiment of the present invention, as shown in FIG. 3, the upper and lower substrates 30 and 40 face each other with the liquid crystal layer 35 interposed therebetween. The common electrode 31 is formed on the inner side of the upper side, and the pixel electrode 41 is formed on each pixel area of the upper side of the lower substrate 40.

In addition, first and second electrical insulating layers 32 and 42 are formed on upper portions of the upper and lower substrates 30 and 40 including the common electrode 31 and the pixel electrode 41, respectively. First and second alignment layers 33 and 43 are formed on the inner upper entire surface of the upper and lower substrates 30 and 40 including the first and second electrical insulating layers 32 and 42.

In addition, upper and lower polarizing plates 34 and 44 are formed at upper portions of the upper and lower substrates 30 and 40, respectively.

The common electrode 31 and the pixel electrode 41 may be formed of indium tin oxide (ITO), tin oxide (TO), indium zinc oxide (IZO), or indium tin zinc oxide (ITO). It is composed of a transparent conductive film such as Indium Tin Zinc Oxide (ITZO), and is formed to have a thickness of about 1000 to 1500 Å.

The first and second alignment layers 33 and 43 are made of an organic material such as polyimide or a photo-alignment material, and have a thickness of about 700 to 1000 GPa.

When the first and second alignment layers 33 and 43 are made of polyimide, the orientation direction is determined by mechanical rubbing, and is made of a polyvinylcinnamate based material or a polysiloxane based material. In the case of the photoreactive material, the orientation direction is determined by irradiation with light such as ultraviolet rays.

At this time, the alignment of the liquid crystal is determined by the irradiation direction of light or the property of the irradiated light, that is, the polarization direction.

The first and second alignment layers 33 and 43 not only determine the alignment direction of the liquid crystal, but also apply a voltage to the pixel electrode 41 and the common electrode 31 for driving the liquid crystal. This prevents leakage current from occurring.

However, as described above in the related art, the first and second alignment films 33 and 43 have a problem of poor insulation compared with the inorganic insulating film.

In order to compensate for the problem of poor insulation of the first and second alignment layers 33 and 43 as described above, in the present invention, before forming the first and second alignment layers 33 and 43, the common electrode 31 and the pixel electrode ( 41) First and second electrical insulating layers 32 and 42 were formed on the upper side, respectively.

As described above, when the voltage is applied to the common electrode 31 and the pixel electrode 41 for driving the liquid crystal, the first and second electrical insulation layers 32 and 42 do not generate leakage current to the liquid crystal layer 35. In order to prevent this, it is configured as an inorganic insulating film having good insulating properties, and the thickness thereof is configured to be approximately 50 to 100 GPa or less.

In detail, although not shown in the drawing, the first and second electrical insulation layers 32 and 42 are not formed by using separate deposition equipment, and form the common electrode 31 and the pixel electrode 41. In the equipment, the valve may be adjusted so that only the O 2 gas flows in the equipment on which the common electrode 31 and the pixel electrode 41 are deposited, so that the inorganic oxide film such as SiO ₂ may be formed.

The above configuration is applicable to not only the TN mode but also the IPS mode.

Although not shown in the drawings, in the liquid crystal display device of the present invention, a plurality of gate lines are arranged in one direction at regular intervals on the lower substrate 40, and are arranged in a direction perpendicular to the gate lines. A plurality of data lines are arranged at regular intervals so as to define a pixel, and a pixel electrode 41 is formed in each pixel region P defined by crossing the gate line and the data line, and the gate line and the data line The thin film transistor TFT is formed at an intersection portion.

In addition, the upper substrate 30 has a black matrix layer for blocking light in portions other than the pixel region P, and R, G, and B color filter layers for expressing color colors are formed, and the color filter layer The common electrode is formed on the front surface including the image. In the IPS mode, the common electrode is formed on the lower substrate 40.

The upper and lower substrates 30 and 40 presented above are merely examples and are not intended to limit the present invention and may have various configurations.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the above embodiments, but should be defined by the claims.

The liquid crystal display according to the present invention as described above has the following effects.

First, by forming the first and second electrical insulating layers composed of inorganic insulating layers on the upper and lower substrates including the common electrode and the pixel electrode, residual DC is generated or ions are generated in the liquid crystal layer between the upper and lower substrates due to leakage current. It is possible to stabilize the liquid crystal drive by preventing the generation of impurities.

Second, by providing the first and second electrical insulating layers, the thickness of the first and second alignment layers can be reduced, thereby reducing the material cost.

Third, since the first and second electrical insulation layers can be formed using the same equipment only by adjusting the valves of the equipment in which the common electrode and the pixel electrode are sputter-deposited, the process can be simplified.

Claims (8)

Upper and lower substrates facing each other with a liquid crystal layer therebetween; A common electrode formed on an inner upper portion of the upper substrate; A pixel electrode formed in each pixel area on the inner upper side of the lower substrate; First and second electrical insulating layers formed on the common electrode and the pixel electrode of the upper and lower substrates, respectively; And first and second alignment layers formed on the entire inner upper surface of the upper and lower substrates including the first and second electrical insulating layers. The method of claim 1, And the first and second electrical insulating layers comprise an inorganic insulating film. The method of claim 1, And the first and second electrical insulating layers have a thickness of 50 to 100 kPa or less. The method of claim 2, And the first and second electrical insulating layers are made of an inorganic oxide film. The method of claim 1, The pixel electrode is formed to have a thickness of about 1000 ~ 15001. The method of claim 1, And the first and second alignment layers have a thickness of about 700 to about 1000 GPa. The method of claim 1, The common electrode and the pixel electrode may be formed of indium tin oxide (ITO), tin oxide (TO), indium zinc oxide (IZO), or indium tin zinc oxide (ITZO). Liquid crystal display device comprising a transparent conductive film, such as). The method of claim 1, And the first and second alignment layers are made of organic material such as polyimide or photo-alignment material.

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